This invention generally relates to a transmission. More particularly, the present invention pertains to a transmission which can change the output direction from the engine through operation of a clutch mechanism.
FIG. 5 illustrates a known transmission 100 that includes an input shaft 111, a rotational member 111A, clutch drums 115, 116, gears 117, 118, clutch mechanisms 121, 122, an output shaft 123, and a gear member 24 (i.e., a gear member for gear shift). The input shaft 111 is in spline engagement with the rotational member 111A for unitarily rotating. The clutch drums 115, 116 extend axially in the right and left direction from the rotational member 111A. The gears 117, 118 are positioned so as to be separated in the axial direction, with the two clutch drums 115, 116 and the rotational member 111A positioned therebetween and with the rotational member 111A being sandwiched between the clutch drums 115, 116. The clutch mechanism 121 is positioned between the rotational member 111A and the gear 117, and the clutch mechanism 122 is positioned between the rotational member 111A and the gear 118. The gear 118 is directly engaged with the output shaft 123 while the gear 117 is operatively connected with the output shaft 123 via the gear member 124. By controlling the hydraulic pressure supplied between pistons and clutch drums 115, 116, the engagement and disengagement between the clutch drums 115, 116 and the gears 117, 118 is switched to thus perform the gear shift.
In the known transmission having the structure described above, two clutch drums 115, 116 are positioned between the gears 117, 118 because the single rotational member 111A is provided as a common wall for the clutch drums 115, 116 which project axially in opposite directions from the rotational member 111A. According to this structure, the length from the right end of the gear 117 to the left end of the gear 118 in the axial direction is longer than the length from the right end of the clutch drum 115 to the left end of the clutch drum 116. In accordance with this, the axial length of the gear member 124 is inevitably longer. In addition, the longer the length of the gear member 124 in the axial direction, the heavier the weight of the gear member 124. Thus, the manufacturing cost is increased, and the size of the transmission as a whole is increased.
A needs thus exists for a transmission in which the size is reduced as well as the cost of manufacture.
A needs also exists for a transmission in which the length of the gear member in the axial direction is shortened.
According to one aspect of the invention, a transmission includes a first shaft adapted to receive an output torque from an engine, a first rotational member coaxially provided with respect to the first shaft for unitarily rotating with the first shaft, a first gear coaxially provided with respect to the first shaft for rotating relative to the first shaft, a first clutch mechanism for engaging and disengaging the first rotational member and the first gear, a second rotational member coaxially provided with respect to the first shaft for unitarily rotating with the first shaft, a second gear coaxially provided with respect to the first shaft for rotating relative to the first shaft, a second shaft for engaging with the second gear, a second clutch mechanism for engaging and disengaging the second rotational member and the second gear, and a gear member having a first gear portion and a second gear portion for gear shifting. The first gear portion is engaged with the first gear and the second gear portion is engaged with the second shaft. At least one of the first gear and the second gear is positioned between the first rotational member and the second rotational member.
In accordance with another aspect of the invention, a transmission includes a first shaft receiving an output torque from an engine, a first rotational member coaxially positioned with respect to the first shaft and rotatable together with the first shaft, a first gear coaxially positioned with respect to the first shaft and rotatable relative to the first shaft, a first clutch mechanism for engaging and disengaging the first rotational member and the first gear, a second rotational member coaxially positioned with respect to the first shaft and rotatable together with the first shaft, a second gear coaxially positioned with respect to the first shaft and rotatable relative to the first shaft, a second shaft engaged with the second gear, a second clutch mechanism for engaging and disengaging the second rotational member and the second gear, and a gear member having a first gear portion and a second gear portion for effecting gear shifting, with the first gear portion being engaged with the first gear and the second gear portion being engaged with the second shaft. The first gear is axially located between the first and second rotational members.
According to another aspect of the invention, a method of assembling a transmission includes press-fitting a first bearing onto the inner periphery of a first gear, assembling a first spring, a first piston, the first bearing and the first gear to a first rotational member, and inserting the first rotational member onto a first shaft, with an inner peripheral portion of the first rotational member and an outer periphery of the first shaft being connected with a spline engagement. A sleeve is inserted into a clearance between the first rotational member and the first shaft. The method also includes press-fitting a second bearing onto the inner periphery of a second gear, assembling a second piston, a second spring and the second gear to a second rotational member, and inserting the second rotational member onto the first shaft. The outer periphery of the first shaft and the inner periphery of the second rotational member are connected with a spline engagement. The second rotational member is inserted until contacting a projection projecting in the radial direction on the first shaft.